This kind of stuff always grossed me out, but whatever, it's not my back.

I saw an episode of "Ripley's believe it or not" like a year or so ago that displayed some of that stuff, One of the "instructors" of it taught his student this type of "body art" as a form of zen which should relax and calm them.

At a bar I go to they have a group of people who come do this the night before halloween every year.